The immune system mediator, IFN-?, is a critical part of the anti-viral defense and it is casually linked to lethal septic shock and some autoimmune diseases. Increased understanding of how IFN-? is regulated by our cells is a key step toward creating better remedies to treat septic shock and autoimmunity. This investigation, designed to yield new information about the regulation of IFN-?, contributes to that goal. Acute inflammation is an early immune response to infection that aids in microbial clearance. Macrophages (Mo) at the infected site trigger the inflammatory response by secreting cytokines. The long-term objective of this research is to understand the molecular mechanisms that regulate the production of cytokines by Mo. Interferon-beta (IFN-?) is a cytokine produced by Mo and other cells that functions in anti-viral defense as well as modulates immune responses that cause autoimmunity. Expression of IFN-? in Mo is primarily controlled transcriptionally. In resting Mo, transcription of IFN-? is repressed, but upon infection, mRNA synthesis is induced. Many of the proteins that bind to the IFN-? promoter and transactivate this gene are well known, while the components that repress transcription are less well characterized. Recently, we discovered that the transcriptional regulator, Activating Transcription Factor 3 (ATF-3), represses IFN-? transcription. Mo lacking ATF-3 or expressing reduced amounts of ATF-3 produce higher levels of IFN-? mRNA after IPS stimulation, compared to wild type Mo. These observations lead us to hypothesize that ATF-3 binds to the IFN-? promoter and represses transcription of this gene in Mo. The specific aims are designed to test this hypothesis by: (1) determining whether over-expression of ATF-3 in Mo represses IFN-? transcription;and (2) determining whether ATF-3 binds to the IFN-[unreadable] promoter;(3) determining whether ATF-3-mediated repression of IFN-? transcription is caused by histone deacetylation. To test for ATF-3-mediated repression of IFN-? transcription, ATF-3 will be over-expressed and IFN-? transcription will be measured in a reporter assay. In vivo binding of ATF-3 to the IFN-? promoter will be tested by chromatin immunoprecipitation (ChlP). The possibility that repression of IFN-? transcription by ATF-3 is caused by histone deacetylation will be tested by examining the acetylation state of IFN-? promoter histones in the presence or absence of ATF-3 by ChlP.